NATIONAL CERTIFICATE (VOCATIONAL) ELECTRONIC CONTROL AND DIGITAL ELECTRONICS NQF LEVEL 2 SUPPLEMENTARY EXAMINATION 2010

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2010 (12041022) 19 February (Y-Paper) 13:00 16:00

1 NATIONAL CERTIFICATE (VOCATIONAL) ELECTRONIC CONTROL AND DIGITAL ELECTRONICS NQF LEVEL 2 SUPPLEMENTARY EXAMINATION 2010 ( ) 19 February (Y-Paper) 13:00 16:00 Calculators may be used. This question paper consists of 6 pages.

2 ( ) -2- NC770(E)(F19)V TIME: 3 HOURS MARKS: 100 INSTRUCTIONS AND INFORMATION Answer ALL the questions. Read the questions carefully and answer only what has been asked. Number the answers according to the numbering system used in this question paper. Questions may be answered in any order, but subsections of questions must NOT be separated. Rule off across the page on completion of each question. Clearly cross out work that you do not want to be marked. Write neatly and legibly.

3 ( ) -3- NC770(E)(F19)V SECTION A QUESTION 1: COMPONENTS 1.1 A breadboard is used as a quick and easy method for building a temporary electronic circuit. Make use of a neat, labelled schematic diagram of a TOP VIEW of the breadboard to indicate and explain its layout and connections. (10) 1.2 An analogue millimetre can be used to measure voltage in an electrical circuit. Name FIVE important elements/features of this instrument. 1.3 The resistance is that which tends to limit or oppose the flow of electrical current and the resistivity of the material or conductor depends mainly on four factors. What are these FOUR factors? 1.4 Fixed inductors look similar to resistors and have their values indicated by a colour code similar to that of resistors. Determine the value of a 4-band colour-coded inductor if its bands from left to right are Violet, Orange, Gold and Yellow. 1.5 A transistor is a solid-state electronic device used for switching and amplification. List the THREE leads of the transistor. 1.6 An operational amplifier (Op Amp) is an integrated circuit containing a number of transistors and other electronic components Name the TWO different types of the 741 Op Amp package. Which ONE of the two types is more commonly available? [30]

4 ( ) -4- NC770(E)(F19)V QUESTION 2: CIRCUIT DIAGRAMS 2.1 The inductance of a coil depends on how it is wound, as well as on four other factors. List these FOUR factors. 2.2 Two inductors of values 5 mh and 20 mh are firstly connected in parallel. This combination is then further linked in series with a third inductor of 6 mh Determine the value of the total inductance of the parallel-series circuit. Make a neat, fully labelled schematic diagram of THREE capacitors that are connected in parallel. The values of the capacitors are 6 µf, 9 µf and 5 µf respectively. Calculate the total capacitance of the circuit in QUESTION 2.3 above. Define a resistor. [15] TOTAL SECTION A: 45 SECTION B QUESTION 3: BINARY THEORY AND FLIP-FLOPS Make use of binary theory to convert to the decimal number system. The process of converting decimal numbers to a binary code is known as encoding. Design and draw a complete encoder to code from decimal to the 8421 BCD code. Subtract the binary number from and convert the answer to a decimal. When the R input of a normal RS master slave flip-flop is connected to the S input via an inverter a D-type flip-flop is obtained. (10) Draw a fully labelled IEC symbol of a D-type flip-flop. Develop a truth table for the D-type flip-flop. (6) 3.5 What is the modulus of a counter? [30]

5 ( ) -5- NC770(E)(F19)V QUESTION 4: BASIC COMPUTER COMPONENTS 4.1 The computer, as most of us know, is a collection of devices that function as a unit. Name FOUR such devices/components that are found inside the tower case of a computer system. 4.2 A 'port' serves as an interface between the computer and other computers or devices. Name TWO ports found on a computer. 4.3 The compact disk (CD) was initially developed for the music industry, but has since been enhanced to be used also as a data storage device. What are the THREE main types of CDs found in the computer industry? 4.4 Non-volatile memory retains its stored data even when electrical power is removed. Give THREE examples of non-volatile memory. 4.5 Why, in your opinion, is a flash memory (also known as a 'memory stick') becoming a more and more popular data storage device? Highlight at least THREE features. [15] TOTAL SECTION B: 45 SECTION C QUESTION 5: TRANSDUCERS USED IN PROCESS CONTROL 5.1 Indicate whether the following statements are TRUE or FALSE. Write only 'true' or 'false' next to the question number ( ) in the ANSWER BOOK Digital signals are used in devices such as calculators. An analogue signal is a voltage or current that is either high or low. In a 4-bit D/A converter the values of the input resistor are chosen to be directly proportional to the binary weights of the corresponding input bits.

6 ( ) -6- NC770(E)(F19)V When using a CD player the digital processor converts the amplified audio signal to binary codes. A successive approximation type A/D converter is much faster than the counter type A/D converter What THREE factors determine the capacity of a capacitive transducer? A Linear Variable Differential Transformer (LVDT) is a transducer that can be used to measure anything moving to and fro. State TWO applications of an LVDT. [10] TOTAL SECTION C: 10 GRAND TOTAL: 100

NATIONAL CERTIFICATE (VOCATIONAL) ELECTRONIC CONTROL AND DIGITAL ELECTRONICS NQF LEVEL 2 NOVEMBER 2009

NATIONAL CERTIFICATE (VOCATIONAL) ELECTRONIC CONTROL AND DIGITAL ELECTRONICS NQF LEVEL 2 NOVEMBER 2009 (12041022) 30 October (Y-Paper) 13:00 16:00 Calculators may be used. This question paper consists